The utility clamp currently used in most scientific laboratories was patented in 1933 by E. H. Fisher, U.S. Pat. No. 1,895,156. The Fisher clamp comprises a pair of opposed jaws pivotally connected at one end to an arm, an external spring disposed between the jaws to urge them apart, and adjustment means, such as a pair of thumb screws, for selectively positioning the jaws relative to each other. The spring is a torsion spring coiled around the outside of the hinge pin. This basic design has proved very useful for most laboratory applications over the years and has changed very little since 1933.
A laboratory utility clamp, such as the clamp disclosed by Fisher, is likely to contact deleterious agents such as acids and other caustic solvents which corrode and contaminate the clamp's critical elements such as the hinge pin and coil spring. While the arms and bracket of the Fisher clamp enshroud the sides of the spring and hinge, the spring and hinge are exposed on the face proximal to the workpiece positioned in between the jaws. During normal use of the clamp, contaminants contact and corrode the spring and hinge pin causing the hinge to seize and/or the spring to prematurely fail, or otherwise adversely affect the performance of the clamp.
Additionally, the bracket or yoke which houses the hinge pin on the Fisher clamp and other prior art utility clamps projects outwardly toward the workpiece and occupies the throat i.e. the empty space in between the jaws. Since the bracket reduces the size of the throat, the clamping capacity of the clamp is limited on complicated structures.